Phase III Copanlisib in Rituximab-refractory iNHL

Inclusion Criteria: * Histologically confirmed diagnosis of indolent B-cell NHL, with histological subtype limited to the following: * Follicular lymphoma (FL) grade 1-2-3a. * Small lymphocytic lymphoma (SLL) with absolute lymphocyte count \< 5 x 10\*9/L at the time of diagnosis and at study entry. * Lymphoplasmacytoid lymphoma/Waldenström macroglobulinemia (LPL/WM). * Marginal zone lymphoma (MZL) (splenic, nodal, or extra-nodal). * Patients must have received two or more prior lines of treatment. A previous regimen is defined as one of the following: at least two months of single-agent therapy, at least two consecutive cycles of polychemotherapy, autologous transplant, radioimmunotherapy. * Prior therapy must include rituximab and alkylating agents.Prior exposure to idelalisib or other PI3K inhibitors is acceptable (except to copanlisib) provided that there is no resistance. * Patients must be refractory to the last rituximab-based treatment, defined as no response or response lasting \< 6 months after completion of treatment. Time interval to assess refractoriness will be calculated between the end date (last day) of the last rituximab-containing regimen and the day of diagnosis confirmation of the subsequent relapse. * Patients must have at least one bi-dimensionally measurable lesion (which has not been previously irradiated) according to the Recommendations for Initial Evaluation, Staging, and Response Assessment of Hodgkin and Non-Hodgkin Lymphoma: The Lugano Classification. * Patients affected by WM, who do not have at least one bi-dimensionally measurable lesion in the baseline radiologic assessment, must have measurable disease, defined as presence of immunoglobulin M (IgM) paraprotein with a minimum IgM level ≥ 2 x upper limit of normal (ULN)and positive immunofixation test. * ECOG performance status ≤ 1 * Adequate bone marrow, liver and renal function Exclusion Criteria: * Histologically confirmed diagnosis of FL grade 3b. * Chronic lymphocytic leukemia (CLL). * Transformed disease (assessed by investigator): * histological confirmation of transformation, or * clinical and laboratory signs: rapid disease progression, high standardized uptake value (SUV) (\> 12) by positron emission tomography (PET) at baseline if PET scans are performed (optional). * Bulky disease - Lymph nodes or tumor mass (except spleen) \>= 7cm LD (longest diameter) * Known lymphomatous involvement of the central nervous system. * Uncontrolled arterial hypertension despite optimal medical management (per investigator's assessment). * Type I or II diabetes mellitus with HbA1c \> 8.5% at Screening. * Known history of human immunodeficiency virus (HIV) infection. * Active clinically serious infections \> CTCAE Grade 2 * Active Hepatitis B or hepatitis C * History or concurrent condition of interstitial lung disease of any severity and/or severely impaired lung function (as judged by the investigator) * History of having received an allogeneic bone marrow or organ transplant * Positive cytomegalovirus (CMV) PCR test at baseline * Pregnant or breast-feeding patients